What is the locus of a surface when r coordinate and phi(φ) coordinate is constant in Spherical coordinate system?

We know that, r=constant is a sphere having radius r. And phi(φ)=constant is a vertical half plane.

So the intersection of these two planes is a line along theta (θ).

As theta (θ) is an angle up to , so the line along theta (θ) is nothing but a semicircle or semicircular line as shown in figure.